const  mongoose = require('mongoose');
module.exports = new Promise((resolve,reject)=>{
    mongoose.connect('mongodb://localhost:27017/studeng_liu',{
        useNewUrlParser:true,useUnifiedTopology:true,useCreateIndex:true});
        mongoose.connection.once('open',err=>{
            if(!err){
                console.log('数据库连接成功！');
                resolve();
            }else {
                console.log(err);
                reject(err);
            }
        })
})